Silk fibroin is a very promising biomedical material because of its renewability, nontoxicity, biocompatibility, and biodegradability. On the basis of a simple and mild method for the preparation of silk fibroin nanospheres with controllable size, the authors developed earlier, anti-cancer drug paclitaxel (PTX)-loaded silk fibroin nanospheres ranging from 270 to 520 nm were produced accordingly. The drug loading, encapsulation efficiency, and released property of PTX-loaded silk fibroin nanospheres are depended on the silk fibroin concentration and initial PTX-loading capacity. The maximum drug loading is about 6.9% and the release time of such a kind of nanospheres is over 9 days. The release time of PTX-loaded silk fibroin nanospheres can be as long as 2 weeks when the drug loading is about 3.0%. All these results imply that such a kind of biomacromolecule-based anti-cancer drug nanocarrier has a great potential for chemotherapy in clinical applications. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2012.